Advice
RHS Help & Advice
Plum pruning
Early summer is the best time to prune plum trees to avoid infection by silver leaf disease. Growing them as a fan or a pyramid is useful where space is limited
Images: Tim Sandall
Minimising disease risk
Although plum trees are getting ready to crop in early summer, it is important to prune them at this time instead of during the dormant season. Pruning cuts expose the plant to the risk of infection by silver leaf disease; most of the spores of this fungal pathogen are released during wet and cool winter weather. Pruning in summer, when there are not so many spores around, minimises the risk of the disease entering through the pruning cuts. To further reduce the risk, treat each cut with a proprietary wound paint and disinfect pruning tools between trees.
Plum trees
Pruning of plum trees does not need to be as frequent nor as precise as for apples and pears. It can usually be limited to removing crossing, weak, vertical and diseased material. Thin the tree out further, if it still appears crowded, by removing three or four branches back to a natural fork. Thinning of branches on old, neglected plum trees should be staged over several years. Aim for a well-balanced tree with an open centre. Trees respond to larger pruning cuts by sending up a mass of new shoots. Where this happens the shoots will need to be thinned in the summer to leave just one or two.
Fan-trained and pyramid plums
When pruning an established fan-trained plum remove any dead, diseased or damaged shoots and, if necessary, some of the older wood if there is a strong young shoot lower down to tie in to fill in gaps in the fan shape.
In summer, prune and train the fan to keep its shape well defined. All new sideshoots should be pinched or cut back to six leaves (left), with regrowth pinched out at one leaf.
After fruiting in late summer, shorten these pruned shoots again to one leaf. This allows the tree to direct its energies into next year’s fruit buds.
For plums that are grown as pyramids (left) shorten new shoots on main stems to 20cm (8in) and strong sideshoots to 15cm (6in).
Helen Bostock